The genome of Mycobacterium tuberculosis codes for two large families of glycine rich proteins namely PE and PPE [1]. The names PE and PPE derive from the motifs Pro-Glu (PE) and Pro-Pro-Glu (PPE) found near the N-terminus of these proteins. Both the families have a conserved N-terminal domain followed by a C-terminal domain which varies in sequence and length. The PE family of proteins is divided in several subfamilies, the largest of these being the repetitive PGRS class, which contains 61 members. The PGRS proteins have a high Glycine content which arises as a result of multiple repetitions of Gly-Gly-Ala or Gly-Gly-Asn motifs. The 69 members of the PPE family have a conserved N-terminal domain followed by C-terminal segments that vary markedly in sequence and length. The PPE proteins fall in three groups, one of which has the MPTR subgroup marked by the presence of tandem copies of Asn-X-Gly-X-Gly-Asn-X-Gly (SEQ ID No. 6). The second group has a conserved motif at position 350 whereas third subgroup proteins have a common PPE domain. A few studies have suggested the functional importance of the PE/PPE [1, 2] family of proteins and it is widely believed that these proteins could be a source of antigenic variation in Mycobacterium tuberculosis [3-7]. Subcellular fractionation and immunoelectron microscopy studies have revealed that some of the members of the PE/PPE family are located on the cell wall fraction of Mycobacterium tuberculosis [8, 9].